1. Field of the Invention
The present invention relates to a mechanism which is compliant and stable in two positions, and which is particularly well suited for use with electrical switches. More particularly, the present invention relates to a mechanism having a plurality of segments coupled end-to-end in series with at least two rigid segments and at least one flexible and resilient segment.
2. Prior Art
Switches are used to activate or adjust an electrical or mechanical system. A toggle switch is one that permits adjustment only to a certain limited number of settings; a bistable switch is further limited in that only two settings are available. As such, bistable switches are very useful for electric circuits, in which it is desirable to open a circuit to cut off the power to an electric device, thereby turning it off. Bistable switches are similarly useful in mechanical systems where the switch is to maintain the system in one of two states.
Many different bistable toggle switches have been invented. The majority are either of the push-button type, such as jumper switches for fuse boxes, the rotary type, as found in many appliances such as stoves and ovens, or the rocker type, which are most commonly mounted on walls to control household electric devices. Both types of switches are in wide use in electrical applications. Switches include some surface or member situated for the transmission of external forces into the switch. In the case of an ordinary household light switch, for example, this can take the form of a post designed to be pushed up or down by a hand or finger. Additionally, mechanical joints such as hinges often require a bistable rocking, rotating, or translating action; this can be accomplished by a bistable switch mechanism. Although the switches are typically inexpensive and small in size, the large number of these switches in common use provides the incentive for reduction of the costs involved in manufacturing them.
Many switches function using some type of linkage to transform the input force to the desired output motion. A linkage is a mechanical system made up of four or more members, or links, which are connected to each other by means of joints that allow the links to pivot or slide with respect to each other. Traditionally, the links were rigid and the joints between them utilized pinned joints, sockets, or mechanical sliders to effect the relative motion. The length of the links and the nature of the joints could be adjusted to obtain the desired output motion in one link from a given input motion or force on another link.
Such a linkage system can be made bistable by the insertion of a device that exerts a linear or torsional force on a sliding or pivoting joint, respectively. These devices are often simple springs; the stable linkage positions are those in which the spring deflection is at a relative minimum. Therefore, the stable points for the linkage system are those in which motion of the linkage in either direction will increase the total potential energy stored in the mechanisms.
There are many disadvantages associated with traditional mechanical linkage systems. One disadvantage with traditional mechanisms is that the links must be separately made and assembled with the joints; as a result, the cost of manufacturing linkages on a large scale is considerable. In addition, there are the usual difficulties associated with surfaces that slide against each other. These difficulties include wear, friction losses, and the need for lubrication.
Therefore, it would be advantageous to develop a bistable mechanism capable of movement between two stable positions. It would also be advantageous to develop such a bistable mechanism capable of simple and inexpensive manufacture. It would also be advantageous to develop such a bistable mechanism with a reduced number of parts. It would also be advantageous to develop such a bistable mechanism with few or no wear surfaces. It would also be advantageous to develop such a bistable mechanism capable of use with electrical switches.